The invention relates to a liquid crystal device comprising a ferroelectric liquid crystal medium between two supporting plates provided with electrodes, which device has an adjustable light transmissivity.
Such a device is suitable, for example as a light shutter.
The invention also relates to a display device comprising a ferroelectric liquid crystalline medium between first and second supporting plates, the first of which comprises a system of row electrodes and the second comprises a system of column electrodes, the crossings of row and column electrodes defining pixels.
Such a device is suitable for passively driven matrices having large numbers of lines, such as TV, and datagraphic applications.
A display device of this type is described in EP 0,214,857. In this device the desired transmission states (representing a grey scale) are obtained by switching on a pixel in n successive fields during a weighted period, dependent on the desired transmission value. This means that a picture memory is required and notably in video applications the ferroelectric liquid crystalline medium must switch n times as fast as would be necessary if grey scale could be achieved more directly. Moreover, during the second and subsequent selected fields the pixel is never completely switched on, which leads to loss of brightness.